Abstract
Several studies have recommended the incorporation of environmental fluctuations in indoor experiments if closer-to-natural results in plant experiments are desired. Previous authors have suggested that if these fluctuations are not applied in synchrony, a stress effect could be present since plants have evolved to cope with synchronic environmental fluctuations. This study aimed to identify the effect of disparity in fluctuations of two important environmental variables, light quantity and temperature, on the growth of seven plant species from different functional plant types. A full-factorial combination of light and temperature under fixed or variable conditions was applied in phytotrons, and plant performance under these conditions was compared with a previous field trial. In all phytotron treatments, the average light and temperature conditions were the same as in the initial field trial. Productivity, leaf gas exchange, chlorophyll fluorescence, pigmentation, and other leaf traits were recorded in all species at the end of the experiments. Most plant trait responses were highly dependent on species and treatment, but some general trends were observed. Light fluctuations were mainly responsible for increases in specific leaf area (SLA) and chlorophyll a concentration, as well as for reductions in total dry weight and chlorophyll a/b ratio, independent if in combination with fluctuation or fixed temperatures. When fixed light conditions were combined with variable temperatures, the plants showed on average lower Fv/Fm values, Amax, and CO2 yield, while under variable light conditions and fixed temperatures, Fv/Fm increased compared with fully fixed or variable conditions. Although significant differences of plant traits between the field trial and all phytotron treatments were present (likely due to differences in other parameters that were not controlled in the phytotrons), our results still suggest that a synchronous variation of environmental factors lead to a more natural-like plant growth than if these factors are fixed or vary asynchronously.
Highlights
Due to the sessility of plants, they are constantly exposed to changes in environmental conditions, and in a plant species’ evolution, it needs to adapt to the site-specific variation in climate
Several studies demonstrated the effects of light and temperature fluctuations on plant traits, where strong effects were generally attributed to daily differences (DIFs) between day and night temperatures
Reference [21] demonstrated in tomato that plant growth can be affected, and the net photosynthesis rate, stomatal conductance, Fv/Fm, quantum yield of PSII chemistry (ΦPSII), and photochemical quenching, which all increased under positive DIF, while Chl a/b ratio and non-photochemical quenching (NPQ) were reduced
Summary
Due to the sessility of plants, they are constantly exposed to changes in environmental conditions, and in a plant species’ evolution, it needs to adapt to the site-specific variation in climate. By employing glasshouses and indoor growth facilities, individuals can grow plants under semi-controlled and controlled conditions, thereby increasing crop yield. Indoor growth facilities are used in plant sciences to grow plants independently of the outside climate, under precisely defined conditions. An absence of climatic variability under indoor conditions can induce unnatural plant growth, and in some cases, these simplified scenarios have led to errors in our predictions of plant–climate relations under natural conditions (e.g., [1,2]). Some authors have proposed several factors that are mainly responsible for unnatural plant growth in indoor growth facilities, including light quantity, plant density, plant age, and the absence of climatic fluctuations [3]
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